1. Field of the Invention
The present invention relates generally to disk drives, and in particular to a method of operating a disk drive including rotating a perpendicular write head to reduce a difference between skew and taper angles.
2. Description of the Prior Art
The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The head disk assembly includes at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA). The spindle motor includes a spindle motor hub that is rotatably attached to the disk drive base.
The head stack assembly has an actuator assembly having at least one transducer head, typically several, for reading and writing data from and to the disk. The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached heads are moved relative to data tracks disposed upon the disk.
In further detail, the head stack assembly includes an actuator assembly, at least one head gimbal assembly, and a flex circuit cable assembly. A conventional “rotary” or “swing-type” actuator assembly typically includes an actuator having an actuator body. The actuator body is configured to rotate on a pivot assembly between limited positions about an axis of rotation. A coil support extends from one side of the actuator body. A coil is supported by the coil support and is configured to interact with one or more permanent magnets to form a voice coil motor. One or more actuator arms extend from an opposite side of the actuator body. To facilitate rotational movement of the actuator, the actuator assembly further includes the actuator body that has a bore and a pivot-bearing cartridge engaged within the bore. Each magnetic disk includes opposing disk surfaces. Data may be recorded on a single surface or both surfaces along data annular regions. As such, the head stack assembly may be pivoted such that each transducer head is disposed adjacent the various data annular regions from adjacent an outer diameter (OD) to an inner diameter (ID) of each disk.
Of particular interest are those transducer heads that include a perpendicular write head. The write head includes a write pole, an opposing return pole and an electrically conductive magnetizing coil disposed about the write pole. The write head includes leading and trailing sides. The leading side of the write head is disposed upon the write pole between the write pole and return pole, and the trailing side of the write head is disposed upon the write pole opposite the leading side.
The magnetic disks that are used with such perpendicular write heads typically include recording media having a hard magnetic recording layer and a soft magnetic underlayer that provide a flux path from the write pole to the return pole. To write to the disk, the write head is separated from the recording media by a distance known as the flying height. The recording media is moved past the write head so that the write head follows the data tracks of disk with the recording media first passing under the return pole and then passing under the write pole. Current is passed through the coil to create magnetic flux within the write pole. The magnetic flux passes from the write pole through the hard magnetic recording layer, into the soft underlayer, and across to the return pole.
Magnetization transitions on the recording media are recorded by the trailing side of the write head and reproduce the shape of the trailing side projection on to the recording media below. During the operation of the disk drive, the slider including its write head travels in an arced path across the disk between the OD and the ID of the disk. This results in a change of skew angle of the slider and its write head in relation to the alignment of the data tracks, with maximum skew angles occurring at either the OD or ID.
Some of the prior art write pole configurations are characterized by a cross section disposed towards the recording media or footprint that is generally rectangular in shape. Thus, the leading and trailing sides on the write pole are the same width. Such a configuration, however, can result in undesirable side erasure problems when the slider is disposed at a skew angle. This is because with the slider skewed the leading side is laterally shifted towards an adjacent data track from that which is currently being written.
Prior art attempts to address this phenomenon have included modifying the cross sectional shape of the write pole to be trapezoidal. In this regard, the leading side is smaller than the trailing side to define a taper angle of the write head. In order to more fully compensate for the skew angle side erasure problem, the taper angle would have to equal the maximum skew angle. However, this has proven to be difficult or impractical to implement due to manufacturing limitations associated with large taper angles. As such, there is a need in the art for an improved disk drive and a method of operating the same in comparison to the prior art.